1. Field of the Invention
The present invention pertains to an apparatus and method of providing high frequency variable pressures to an airway of a patient, and, in particular, to an apparatus and method of providing high frequency variable pressures in which a valve generates the pressure oscillations in the delivery of gas to or from the patient independent of patient effort.
2. Description of the Related Art
Many people have difficulty clearing secretions, such as mucous or fluids, from their respiratory system. In a healthy patient, accumulated secretions are removed from the respiratory system by clearing the throat or coughing. Some patients, however, such as those with a weakened respiratory system, may not be physically able to perform such a secretion clearing movement with sufficient strength to remove or loosen the secretion.
To address this problem, a device is known that creates an abrupt pressure variation in the patient""s airway, particularly during exhalation, to assist in dislodging or removing the secretions. An example of such a device is a hand-held flutter valve, which uses a ball valve to create the pressure oscillations. When the patient breathes into the flutter valve, the force of the patient""s exhalation moves a ball off a valve seat to open the valve. Gravity immediately urges the ball valve back onto the seat to obstruct the patient""s expiratory flow until the expiratory force is sufficient to again urge the ball off of the seat. This process repeats as the patient exhales until the patient""s expiratory force is not great enough to move the ball off of the seat. A series of pressure spikes occur in the patient""s airway as a result of the temporary flow interruption caused by the closing and opening of the ball valve to facilitate loosening and removal of the patient""s airway secretions.
There are disadvantages associated with this flutter valve secretion clearance device. For example, proper seating of the ball on the valve seat is only possible if the device is held in its upright position. Therefore, the conventional flutter valve device is very position sensitive. In addition, because the patient""s own expiratory force is used to move the ball to the open position, the flutter valve cannot be used by patients with very weak respiratory systems who have very low expiratory flow rate.
Another device that provides pressure oscillations to the patient""s airway is the Emerson Cough-a-Lator, produced by Emerson, Inc. This device provides both a positive and a negative pressure to the patient""s airway to assist in secretion clearance. A mechanism in the device physically moves a portion of a patient circuit in a windshield wiper fashion between a first position, where a positive pressure output from a blower is coupled to the patient, and a second position, where a negative pressure at the input of the blower is coupled to the patient. This device is relatively large, complex, bulky and expensive, and, therefore, is not readily portable. It is also generally not convenient or easy to set up and use.
Accordingly, it is an object of the present invention to provide a high frequency pressure oscillation device and method that overcomes the shortcomings of conventional devices, such as the above-described flutter valve. This object is achieved according to one embodiment of the present invention by providing a high frequency pressure oscillation device that includes a patient circuit defining a closed path between a source of breathing gas and the airway of a patient. A valve in the patient circuit moves between an open position and a closed position. In the open position, the path between the source of breathing gas and the patient""s airway is substantially unobstructed. In the closed position, the path between the source of breathing gas and the airway of the patient is at least partially obstructed so that the flow in the path is restricted. An actuating system alternatively places the valve in the open position and the closed position at a predetermined oscillation rate and does so independent of patient effort. Alternatively opening and closing, either completely or partially, the path between the patient""s airway and the source of breathing gas while the patient inhales or exhales through that path generates pressure spikes in the patient""s airway that facilitate loosening and removal of accumulated secretions.
It is yet another object of the present invention to provide a method of providing high frequency pressure oscillations to an airway of a patient that does not suffer from the disadvantages associated with conventional techniques. This object is achieved by providing a method that includes a) providing a patient circuit defining a closed path between a source of breathing gas and an airway of a patient, b) providing a valve in the patient circuit operable to control the flow of gas in the path, c) moving the valve to an open position within the patient circuit to substantially open the path between the source of breathing gas and the patient""s airway, and d) moving the valve to at least a partially closed position within the patient circuit to restrict the path between the source of breathing gas and the patient""s airway either completely or partially. According to the principles of the present invention, moving the valve between the open position and the closed position is accomplished independent of patient effort. Steps c) and d) are repeated to alternatively place the valve in the open and the closed positions at a predetermined oscillation rate. As noted above, alternatively opening and closing the path between the patient""s airway and the source of breathing gas while the patient inhales or exhales through that path generates pressure spikes in the patient""s airway that facilitates loosening and removal of accumulated secretions.
It is a further object of the present invention to provide the above-described secretion clearance device in combination with the functions of a conventional spirometer, so that a single device provides both a secretion clearance function and a pulmonary monitoring function. This object is achieved by providing the above-described secretion clearance device in combination with a pulmonary measurement system, such as a flow sensor, associated with the patient circuit. The pulmonary measurement system is capable of functioning as a spirometer that measures a characteristic associated with a pulmonary function of a patient, such as the rate of flow of gas through the patient circuit. In a further embodiment of the present invention, a mode selection switch is provided that allows a user to select between (1) the secretion clearance mode, in which the actuating system alternatively places the valve in the open position and the closed position at a predetermined oscillation rate to clear secretions from the airway as described above, and (2) a spirometer mode, in which the valve remains in the open position and the pulmonary measurement system measures a characteristic associated with a pulmonary function of a patient.
These and other objects, features and characteristics of the present invention, as well as the methods of operation and functions of the related elements of structure and the combination of parts and economies of manufacture, will become more apparent upon consideration of the following description and the appended claims with reference to the accompanying drawings, all of which form a part of this specification, wherein like reference numerals designate corresponding parts in the various figures. It is to be expressly understood, however, that the drawings are for the purpose of illustration and description only and are not intended as a definition of the limits of the invention.